1 Computers: Tools for an Information Age Chapter 3 Operating Systems: Software in the Background

2 Objectives Describe the functions of an operating system Explain the basics of a personal computer operating system Describe the advantages of a graphical operating system Differentiate among different versions of Microsoft Windows Explain the need for network operating systems

3 Objectives Describe the methods of resource allocation on large computers Describe the differences among multiprocessing, multiprogramming, and time-sharing Explain the principles of memory management List several functions that are typically performed by utility programs

4 Operating Systems: Hidden Software Serves as intermediary between hardware and applications software Operating System Systems software Kernel

5 Operating System A set of programs that lies between applications software and the hardware Manages computer’s resources (CPU, peripheral devices) Establishes a user interface  Determines how user interacts with operating system Provides and executes services for applications software Return

6 Systems Software All programs related to coordinating computer operations Examples Operating systems Language translators  Convert program code to machine-readable form Utility programs  Perform secondary chores Return

7 Kernel Manages the operating system Loaded from hard drive into memory when computer is booted  Booting refers to starting the computer Loads other operating system programs from disk storage as needed  Other programs referred to as nonresident Return

8 Operating Systems for Personal Computers Platform: combination of computer hardware and operating system software Wintel (Microsoft Windows running on an Intel- based PC) is most common Common Platforms MS-DOS Windows MAC OS Unix Linux

9 MS-DOS Uses a command-line interface Screen provides prompts for user User types commands Largely replaced by graphical user interfaces Not user-friendly Return

10 Microsoft Windows Began as an operating environment for MS- DOSoperating environment Not a full-blown operating system; required MS- DOS Uses a graphical user interfacegraphical user interface Users can use DOS commands and interface Now a complete family of operating systemscomplete family Return

11 MS-DOS Operating Environment Windows 3.1 A layer added “on top” of DOS Separates operating system from user Makes operating system easier to use Called a shell Return

12 Graphical User Interface User clicks an icon to perform tasks Start Menu in lower left corner launches programs Use menus to activate commands Return

13 Windows Features Long file names (up to 255 characters) Plug and Play Makes installing hardware components easier Object Linking and Embedding (OLE) Allows user to embed or link one document to another Return

14 Windows 9x Windows 95 Windows 98 Windows Millennium Edition (ME) Corporate Market Windows NT Windows 2000 Windows XP Windows CE The Windows Family Return

15 Windows 9x Serves home/consumer market No longer a shell, but a self-contained operating system Began with Windows 95 Next Generation:  Windows 98 Windows 98  Windows ME Windows ME Many improvements over Windows 3.1improvements Return

16 Windows 98 Enhancements Internet/intranet browsing capabilities Support for state-of-the-art hardware, including DVD and multimedia Support for huge disk drives Wizards: step-by-step software for installing, configuring, and using software Return

17 Windows ME Enhancements Multimedia support: Media Player, video editing Enhanced reliability features Home network support Return

18 Corporate Market Windows NT NT stands for “new technology” Windows 2000 Return

19 Windows NT Desktop looks and acts like Windows 98 Meant for corporate, networked environments Engineered for scalability (the ability to handle many users) Stronger security Return

20 Windows 2000 The latest generation of Windows NT One computer “serves” many users You identify yourself and the system knows your preferences You get “your” desktop and files, regardless of which PC you use to log into the network Return

21 Windows XP Brings consumer and corporate versions of Windows together into a single product Has Home and Professional Editions Enhancements Return

22 Windows XP Enhancements Improved user interface Much clearer and uncluttered desktop More icons on redesigned Start Menu Improved multimedia support More personalization Multiple user support User can log off, leaving programs running, and allow another user to log on Set up limited accounts for children to use; i.e., no inappropriate games or no Internet access Internet support and protection Return

23 Windows CE Scaled-back version of Windows 9x Designed to work on machines with small screens and little, if any, storage Used in Pocket PCs Used in embedded systems Computer devices integrated into other products; i.e., robots CE.NET supports.NET platform Return

24 MAC OS Designed for the Macintosh computer First commercially successful GUI Has served as the model for Windows and other GUI products developed since then Return

25 UNIX Developed in 1971 for use on the DEC minicomputer Character-based system with command-line interface Not tied to any family of processors Runs on just about every type of system (PC, mainframe, workstation) from any manufacturer Primary operating system in use on Internet servers Handles many simultaneous users easily Return

26 Linux Uses command-line interface Many companies have created a GUI to work with Linux Open-source concept Source code is free Users can download, change, and distribute the software More stable than Windows Applications relatively scarce Return

27 Operating Systems for Networks Network operating system (NOS) Handles network functionsnetwork functions Make resources appear as though they were running from client computers Common systems

28 Network Functions Sharing resources (hard disks and printers) Data security Troubleshooting Administrative control Return

29 Network Operating Systems Windows NT Server Windows 2000 Server Windows.NET Server Novell Netware Unix Linux Return

30 Operating Systems for Large Computers Resource allocation: assigning and computer resources to certain programs and processes for their use Main issues related to resource allocation Sharing the Central Processing Unit Sharing memory Sharing storage resources Sharing printing resources

31 Sharing the CPU Multiprocessing Multiprogramming Time-Sharing Return

32 Multiprocessing The use of a powerful computer with multiple CPUs Multiple programs run simultaneously Each runs on its own processor Return

33 Multiprogramming Two or more programs executed concurrently Programs take turns using the CPU Event-driven  An interrupt suspends processing to allow another program to run  After the second program runs, the operating system returns the CPU to another program Generally used for batch programs that do not require user input Return

34 Time-Sharing Programs take turns using the CPU Time-driven Each user is given a slice of time (fraction of a second) CPU works only on that user’s tasks during its time slice Response time: the time between typed request and computer’s reply Typically used in applications with many users Return

35 Sharing Memory Memory management Divides memory Divides memory into foreground and background Uses virtual storage Also called virtual memory Return

36 Memory Management Divides memory into separate partitions Allocates memory to programs Keeps programs separate from one another Return

37 Foreground and Background Foreground: for programs with high priority that will receive more CPU time. Background: for programs with lower priority that will receive less CPU time Programs waiting to run are kept in queues based on their priority Return

38 Virtual Storage Programs currently executed are stored on disk Portions of program brought into memory as needed Minimizes the amount of memory needed Can be implemented by paging Divide memory into small, fixed-size pages Page table keeps track of memory locations Return

39 Sharing Storage Resources Keeps track of location of files Responds to commands to manipulate files Keeps track of input and output requests for files Processes them in the order received Return

40 Sharing Printing Resources Spooling: program writes a line to a disk file rather than sending directly to a printer When file is completed, placed in queue File printed when printer becomes available Allows program to complete execution much more quickly Writing to disk much quicker than writing to printer Return

41 Utility Programs Perform secondary chores Examples File manager File compression Others

42 File Manager Stores files in a hierarchical directory structure Windows uses Windows Explorer Return

43 File Compression Reduces amount of space a file requires Makes file take up less space on disk Takes less time to transmit across communication lines Return

44 Other Utility Programs Backup and Restore Backup: make copies of disks and store in a safe place Restore: restore files from backups Disk defragmenter: reorganizes disk so all files are stored in contiguous locations Device driver: handles commands for devices, such as printers and storage devices Return